Around 20 percent of kids will develop one or more compulsive tics, such as excessive blinking, throat clearing or shrugging, at some point during childhood. Yet far fewer (only around 3 percent) go on to develop a chronic tic disorder, such as Tourette syndrome.

In fact, conventional wisdom holds that most of these childhood tics go away on their own.

But evidence from a new study at Washington University School of Medicine challenges this long-held notion: The researchers found that childhood tics may not away completely. Rather, children with tics seem to get better at hiding them when others were watching.

The study involved 45 children (30 boys), ages 5 to 10, who had just started experiencing some sort of tic. All of the children were examined within a few months of when their tics first appeared, and a second time 12 months after the tics had started.

“Our expectation, initially, was that maybe one in 10 kids would still have tics at their follow-up exams,” said first author Soyoung Kim, Ph.D., a postdoctoral research associate in psychiatry. “Most had improved a year later, but to our surprise in every case, the children still had tics — many of them just controlled them better.”

The researchers verified the presence of tics by leaving each child alone in a room with a video camera. They found it was possible for most children to suppress tics when they were being watched during neurological exams. But when left alone, the children exhibited tics, without exception.

“We found that tics were still present one year after they first appeared but that many of the kids we studied had figured out how to suppress them,” said principal investigator Kevin J. Black, M.D., a professor of psychiatry. “Uncovering just how they are able to control these tics may help other children do the same and perhaps avoid chronic tic disorders such as Tourette syndrome.”

The study was able to pinpoint several factors that predicted problematic tics at the one-year mark, as well as factors related to the ability to suppress tics. Having an anxiety disorder history was a predictor of being unable to control or suppress tics, as was having pronounced tics during the kids’ initial exams. Having three or more vocal tics, such as throat clearing or making other noises, also indicated likelihood of evident tics one year later.

In addition, children with higher scores on the Social Responsiveness Scale — a test that measures behaviors on the autism spectrum — also were likely to have continued problems with tics a year after first experiencing them.

“None of these kids had autism, but those who did a little bit worse on that test, who had what we would call sub-syndromal symptoms of autism, were more likely to have trouble with tics one year later,” Black said.

The researchers used a reward system to help determine whether the children could suppress their tics. In one experiment, the children were given a token worth a few pennies for every 10 seconds they could go without having a tic. Those who suppressed their tics most effectively in response to rewards exhibited fewer and less significant problems at their follow-up visits.

“My suspicion is that, over time, these kids may improve in their ability to suppress tics, just from social cues,” Black said.

“But perhaps more importantly, early on — when they’ve experienced tics for only a few weeks or months — some children already can suppress them. If we can develop ways to help other children acquire those skills, we might improve quality of life for those who otherwise may go on to develop a chronic tic disorder such as Tourette syndrome.”